The present invention relates to a liquid crystal display element, and more particularly, to a liquid crystal display element which is suitably used in an apparatus used for display purposes.
FIG. 6 is a cross sectional view which schematically illustrates the construction of a liquid crystal display element 1 according to a prior art device and FIG. 7 is a plan view of this device.
With reference to FIG. 6, in the liquid crystal display element 1, on one of its surfaces, which may be realized by a pair of glass sheets are placed, light transmissive insulated substrates 2 and 3, which may be realized by indium oxide (ITO), and orientation films 7 and 8, which may be realized by polyimido. These glass sheets are laminated with the substrates and films and arranged opposedly, with each film surface of the orientation films 7 and 8 being disposed on the inside of the glass sheets. On one surface of the light transmissive insulated substrates 2 and 3 are placed transparent electrodes 4 and 5 which may be realized by indium oxide (ITO). The electrodes are formed into a plurality of belt-shaped forms, and are covered with interlaminar insulated films 2a and 3a. Sealing members 10a and 10b are interposed between the orientation films 7 and 8. The orientation films are provided with a rubbing treatment so that a liquid crystal molecule 6 is caused to be oriented along one axis with respect to the face to the transparent electrodes 4 and 5. Also, the thickness of the liquid crystal layer 9 which is injected with the liquid crystal molecule 6 is maintained at a constant thickness, and the liquid crystal molecule is sealed inside the device. As a result of this, a liquid crystal cell 11 is formed. A pair of polarizers 12 and 13 are installed to standwich the liquid crystal cell 11 so that, as will be described later, the rubbing angle, which is determined in advance, is formed by the polarized axis of the polarizer and the orientation film when these elements are caused to face each other in a predetermined direction. With respect to the liquid crystal display element, a light source L is irradiated from the back side of the liquid crystal device, as shown in FIG. 6, in a direction indicated by the arrow, that is, in the direction of the upper surface of the liquid crystal device.
With reference to FIG. 7, by sandwiching a liquid crystal layer which is not shown in the diagram, the transparent electrodes 4a, 4b, 4c, . . . , and 4M formed into a plurality of belt-shaped forms (M=1, 2, 3, . . . when general indication of the electrodes 4m is by used as a reference symbol) and the other transparent electrodes 5a, 5b, 5c, . . . , 5N (N=1, 2, 3, . . . when general indication of the electrodes 5N is used as the reference symbol are arranged to intersect at right angles. One of the transparent electrodes which intersect at right angles is generally called a horizontal electrode 4, and the other of the transparent electrodes which intersect at right angles is generally called a vertical electrode 5. 15a, 15b, 15c, . . . are the square portions generated at the intersections of the two electrodes 4 and 5 and are generally called the picture element 15. The liquid crystal layer which is not shown in the diagram is included. Therefore, on the front of the display element 1, the display image 14 is formed by M.times.N pieces of the picture element 15, and a plurality of spaces 16 which is a non-electrode portion existing around an individual picture element 15. In the display image 14, when a voltage is applied across the horizontal electrode 4 and the vertical electrode 5, the picture element 15 at the intersection of the two electrodes lets the light from the light source not shown in the diagram of FIG. 7 to transmit or demonstrate an optical behavior. This optical behavior transmits or shields the light from the light source which is not shown in the diagram.
FIG. 8 is a diagram which shows the absorption axis a1 of the back side polarizer 12 and the rubbing direction b1 of the back side orientation film 7 according to the prior art, and FIG. 9 is a diagram which shows the absorption axis a2 of the surface side polarizer 13 and the rubbing direction b2 of the surface side orientation film 8. As shown in FIG. 8 and FIG. 9, the angle between the absorption axis direction a1 of the back side polarizer 12 and the rubbing direction b1 of the back side orientation film 7 and the angle between the absorption axis direction a2 of the surface side polarizer 13 and the rubbing direction b2 of the surface side orientation film 8 are 45.degree. respectively. The absorption axis direction a2 of the surface side polarizer 13 is rotated 60.degree. in clockwise direction with respect to the absorption axis direction a1 of the back side polarizer 12. In the case where the rubbing directions of the orientation films 7 and 8 and the absorption axis directions of the polarizers 12 and 13 are arranged to oppose each other in a manner such as above, the liquid crystal display unit 1 becomes a bright state when no voltage is applied, while the liquid crystal display unit 1 becomes a dark state and the light is shielded when a voltage is applied.
With reference to FIG. 6 and FIG. 7 again, although the actual position of the picture element 15 shields the light from the light source L when a voltage is applied, the space 16 around the aforementioned picture element 15 is not applied with voltage. Therefore, an inconvenient phenomenon occurs in which the light leaks from this space, causing the contrast of the display screen to weaken. And, in particular, in the case of the color liquid crystal display element in which the color filter is inserted into the liquid crystal cell, there is an inconvenience in which the purity of the display color is reduced together with the contrast.
In order to solve these problems in the prior art, a method was used wherein the space 16 is provided with what is called the black matrix printing so as to fill the space thereby preventing the light from leaking. Also a method was used wherein the thin film transistors for driving which are not shown in the diagram are caused to correspond on a one to one basis to individual picture element 15 so as to be connected by forming a metal wiring which is not shown in the diagram in the space 16 around the picture element 15, so that the metal wiring section is made of a light shielding material.
However, in order to prevent the light leakage from the above-mentioned space 16 and to realize the desired effect, it requires a number of materials and complicated processes as stated above, and further the yield is poor and an increase in production cost is unavoidable. Therefore, a liquid crystal display element whereby the light leakage prevention is realized through simple processes and reduced costs has been realized in the prior art.